For the absorption of both radial and axial stresses it is known to use one or more sets of rotary bodies, i.e. rollers or balls, which are partly received in confronting track grooves of an outer race formed by a bearing sleeve and an inner race which may be constituted by the peripheral surface of the shaft itself.
The shaft of a vehicular water pump, for example, is subjected to torques due to unbalances of the pump motor and other components carried thereon, e.g. a fan, aside from experiencing bending moments due to the stress of the V-belt by which it is driven. The mounting of that shaft, therefore, must be designed to absorb all these stresses while also resisting axial forces, e.g. those resulting from the air pressure upon the fan blades.
In a commonly owned copending application, Ser. No. 76,360 filed 17 Sept. 1979 by Roland Tischer, now U.S. Pat. No. 4,244,630, there has been disclosed a bearing assembly with two sets of rotary bodies, specifically a set of balls and a set of rollers, near opposite ends of a cylindrical shell coaxially surrounding the associated shaft. In order to facilitate the assembly of such a shaft mounting, the shell is divided into two axially spaced bearing rings interconnected by a sleeve of elastomeric material engaging these rings with a snap fit. A bearing with three sets of rotary bodies, namely two outer rows of balls and a centrally disposed row of rollers, is disclosed in Swiss Pat. No. 165,580.
In general, a set of centrally disposed bearing balls or rollers contributes nothing to the absorption of bending moments such as those exerted by a driving belt. Rollers, which tend to stiffen the shaft against radial deflection, are therefore more advantageously placed near an end of a journal bearing as described in the commonly owned application referred to.
Still, the provision of a third set of rotary bodies increases the load-sustaining capacity of the bearing, especially when the surrounding cylinder is of unitary all-metallic structure. Balls guided in track grooves are conventionally used to prevent relative axial shifts of the two races. As long as the combined depth of the two confronting grooves is substantially less than the ball radius, the balls can be readily inserted when the sleeve is eccentrically positioned on the shaft, this operation being followed by a peripheral distribution of the balls in the clearance between the shaft and the sleeve while the latter is being centered on the shaft axis. The balls can then be held separated by an axially introduced annular cage as is well known per se. Only two axially spaced sets of balls, however, can be introduced into a unitary bearing sleeve by this procedure.